Process of coating articles with liquid pyroxylin or the like



Patented Feb. 28, 1933,

' UNITED STATES PATENT OFFICE WILLIAM c. nimr'ron, or DAYTON, c1110,ASSIGNOR TO THE cnnwronn MCGREGOR Ann CANBY COMPANY, or DAYTON, 03 0, ACORPORATION or OHIO PROCESS OF COATING ARTICLES WITH LIQUID IPYROXYLINOR THE LIKE No Drawing.-

rious prior patents describe articles as being coated or encased incelluloid, pyroxylin or analogous material, the actual carrying out ofsuch a process involves numerous difficulties and necessitates specialsteps and handling for which the necessary teaching and instruction isnot found in those prior publications and patents which so nonchalantlyrefer to such use of liquid celluloid and the coating of articles bydipping therein.

In attempting to coat articles by dipping in a liquid pyroxylin ornitrocellulose material, many baffling failures are encountered, Thepresent method and steps to be followed in utilizing such coatingmaterial in liquid form have been discovered only after long experimentand trial. It is quite easy to dissolve the material in a suitablesolvent such as alcohol, ether, acetate or acetone, the latter beingpreferred, and to plunge the article to be coated into such solution,and no difliculty is involved in rotating the article to effectapproximately unif Jrm distribution. However, to effect the properdrying and solidification of the material to afford a uniformly smoothsurface'having a-high natural polish or gloss has been found to beextremely difiicult and to involve careful control of temperatures andhumidity.

The major difficulties encountered are those of moisture condensationupon the coating,

causing it'to become discolored or streaked,

the prevailing-tendency of the coating material while solidifying tobecome wrinkled,

' and the formation of bubbles or pimples, causing the surface to becomeunsightly and,

rough.

The present process overcomes these dif- Application filed m 24, 1929.Serial No. 365,781.

ficulties and enables the uniform coating of articles in commercialquantities wherein the coating is formed in situ. A succession ofarticles may be coated to uniform thiclmess, the depth of which may bequite accurately controlled. The finished product possesses an extremelyhard, smooth, unbroken surface having a quite high degree of polish orgloss Without the necessity of further working or treatment. I

One of the primary objects of the present invention is to afford asurface finish or coating for metal and wooden articles of greatdurability and strength which will not chip,

craze or crack, which can be produced in a wide variety of colors, andwill possess wearing qualities under severe usage superior to the usualpaint, varnish and lacquer finishes.

Whereas shafts, rods and other articles have heretofore been covered orencased by wrapping thereabout strips of celluloid, pyralin or likematerial, or by enclosing such bodies in tubular casings formed fromsheet material which is then subjected to heat and pressure or byplastic molding such material, one of the dominant features of thepresent invention is to apply a surface coating or finish which will beformed in situ and which will unite with and adhere to the coatedarticle with such tenacity that it will not be likely to split or peeltherefrom.

A further object of the invention is to reduce the cost of coating orencasing articles in celluloid, pyroxylin or analogous material.

' A further and important obJect of the invention is to providea'surface coating or finish which will possess a natural high polish orgloss without the necessity of grinding, bufiing,'or burnishing.

A further and important object of the invention is to provide a methodor process for- 1 controlled.

' pear in the specification, the invention consists of the process,steps and treatment and the method of control of the drying orsolidifying of the coating material as hereinafter described or theirequivalents as hereinafter described and set forth in the claims.

The present process is applicable to the coating of articles of variousshapes and in various lines of manufacture, as for example, the coatingof furniture, handles or knobs for various purposes, golf club shafts,fishing rods, polo mallets, tennis racquets and other sporting goods,various articles of household and factory equipment, toilet articles andnumerous other articles of both metal and wood. .For purpose ofillustration, but without intending to limit or otherwise restrict theapplication of the process and invention, it will be described in itsapplication to the coating of tubular metallic golf club shafts to whichit is now being very successfully and extensively applied.

The material employed is obtainable commercially in sheet form, beinggenerally sold under the name of pyroxylin, pyralin, celluloid and othercommercial or trade names for materials having nitrocellulosecharacteristics. Thismaterial is soluble in alcohol, acetone, or someform of acetate. The material is workable at a consistency of thickcream and when dissolved is of viscous character.

The surface to be coated is thoroughly cleansed to remove any grease,dirt or scale. This cleansing is preferably effected by means of a sandblast which gives to the article a slightly roughened or matte surface.It is found that this cleansing and dulling or matting of the surfacegreatly facilitates the adherence of the coating material.

The cleansed article, which for example is a tubular metallic golf clubshaft, being first plugged at its end to prevent entrance of thematerial, is immersed in the liquefied material, which is preferablycontained in tall cans or tanks permitting the shafts to be dippedvertically. The shaft is lowered slowly into the liquid material inorder that air may not be carried downward into the solution by frictionof the shaft surface. After being immersed to the desired extent, whichin the case of golf club shafts is to a point a short distance abovethat at which the grip wrapping begins, it is permitted to remain in thecoating liquid for a short time, sufficient to allow any air bubbles toescape and the ma terial to adhere to the shaft. The shaft is thenwithdrawn and the surplus material allowed to drain back into thereceptacle until the excess material has been removed. The coated shaftis then slowly rotated in order to distribute the material uniformly andprevent a drainage or sagging of the yet soft or semiliquid material toone side of the shaft.

In commercial operation the coated shafts are mounted upon a powerdriven apparatus which transmits to them a slow rotation while theshafts are maintained in an inclined position of a proximately twenty tothirty degrees. A ter the shaft has been rotated a few times todistribute any accumulation of material, water or other temperaturecontrolling medium is discharged through the hollow interior of theshaft while the rotation continues until the material is set orhardened. It is during this stage that the major difliculties areencountered. The solvents employed are more or less volatile, and theevaporation is normally quite rapid. It has been found impractical touse retarding agents, which have a tendency to break down the structureof the material and to lessen its strength. The evaporation of thesolvents under ordinary conditions, is so rapid as to produce arefrigerating effect and the surface of the coating material becomes socold as to cause moisture condensation from the atmosphere thereon. Theaccumulation of water of condensation upon the surface coating distortsand discolors the material. This moisture causes yellow and whitestreaks to appear upon the darker materials, and prevents the formationof the desired polish or gloss. Such attraction of moisture is termedblushing or watering. Under ordinary atmospheric conditions andtemperatures, sufiicient water will be collected to form drops whichtrickle down the surface. Where drops rest, surface pitting also occurs.

The difficulty of bubbling and pimpling occurs when the exterior film ofthe material becomes too quickly set, confining within the body ofmaterial a portion of the solvent which has not had time to evaporateand which under temperature increase, as the refrigerating effect ofsurface evaporation is arrested, expands within the deposit of material,causing the material to swell and form bubbles, pimples and otherirregularities.

The difficulty of wrinkling occurs at a somewhat later stage in theprocedure. Even though the exterior has been maintained sufficientlysoft to permit the escape and evaporation of all of the solvent, if itis then allowed to set or dry too rapidly, the outside surface dryingfirst shrinks, causing displacement and distortion of the underlyingmaterial, causing it to form wrinkles, lines and ridges, giving to thesurface a crinkled appearance. This may be prevented only by controllingthe drying operation so that the material will set or harden slowly anduniformly.

The successful application of celluloid, pyroxylin or analgousnitrocellulose materials in liquid form, is thus to a very considerableextent dependent upon accurate control of temperatures, moisture orhumidity in their relation to barometric pressures. The

work of dip ing and drying must be done in a room of xed temperature andhumidity. This temperature is necessarily rather low to prevent toorapid evaporation of the solvent. 5 The temperature of the thermalmedium circulated through the hollow metallic golf shaft after theremoval of the plug, which may be water, air or other fluid, bears adefinite relationship to the room temperature, being ordinarily aboutfour degrees lower in temperature than that of the roofn. Paradoxical asit may seem, this circulating medium, without change of temperatureWithin itself, is at one stage of the protedure a warming agent, whileat a subsequent stage it becomes a cooling agent. Means may be providedfor dehydrating the air hf the work room, preferably by means ofrefrigeration coils or a chilled surface'lof lower temperature than thework, upon which the condensation will deposit in preference todepositing on the material. The moisture is thus extracted from the air.lVh'en the immersed shaft is lifted from the coating liquid, the rapidevaporation of the solvent very materially lowers the temperature of theshaft and material and would cause collection of condensation orwatering even though the humidity of the air is very low.

For the best results, the room temperature should be maintained at fromfifty to fiftyfour degrees, the lower temperature being preferable. Thetemperature of the con- 'densing, surface coil for the extraction ofatmospheric moisture is maintained at approximately thirty-two degreesFahrenheit. As before mentioned, after the excess material has beendrained from the dipped shaft, the plug in its lower end is removed andit is mounted in a rotating apparatus in connection with a water supplywhich is discharged through the interior of the hollow metallic shaft at'a temperature of approximately forty-six degrees, assuming the roomtemperature to be fifty degrees. That is'to say, the control medium ismaintained at approximately four degrees Fahrenheit below thetemperature of the room. The refrigeratin g affect of the rapidevaporation of the solvent is such that the temperature of the coatingmaterial is temporarily reduced, and during this period. the circulatingwater acts-as a warming medium to counteract such refrigerating effectof the evaporation, which would otherwise cause condensation andwatering upon the partially dried surface of the shaft. The circulationof the temperature control medium maintains the coating mate- .rial atapproximately forty-four degrees coating material, the refrigeratingeffect is arrested. At this stage, the thermal control Fahrenheit, orsufficiently above the. dew

After the solvent is evaporated from the i oftemperature of t e materialto that of the room. The room temperature being maintained comparativelylow, at say fifty degrees Fahrenheit, does not permit rapid drying orsolidification of the surface film of the material and the circulationof the thermal control medium through the tube at a lower temperatureprevents undue expansion of any remaining solvent which would otherwisecause bubbling or pimpling. The water or thermal control mediumcontinues to circulate through the. hollow shaft until the material iswell set and hardened. It is thus maintained at sufficiently lowtemperature that the material hardens uniformly and with uniformshrinkage thereby avoiding the wrinkling of the surface.

By experiment it has been found that the coating process may besuccessfully carried out within a temperature range of the temperaturecontrol medium of forty-two to fiftytwo degrees Fahrenheit, while therange of room temperature may be from fifty-four degrees Fahrenheitdownwardlv to the operating temperature of the control medium. If thetemperature of the room should fall below that of the control medium,the coating is subjected to two cooling effects, i. e., therefrigerating effect of the evaporating solvent and the low roomtemperature, and undesirable effects result. i

The temperatures at which best results are obtained fluctuate withbarometric pressure. At normal barometric reading the preferable roomtemperature is fifty degrees Fahrenheit, and the temperature of thecirculating thermal control medium is preferably forty-six degrees. Asthe barometric pressure rises, these temperatures will relatively riseand at a high barometric reading of 29.30 to 29.50 a room temperature offifty-three to fifty-four degrees Fahrenheit and a temperature of thethermal control medium of forty-eight degrees Fahrenheit is productiveof good results. The variation of barometric pressures has a markedinfluence upon the rate of terial must be maintained below the point atwhich any solvent yet remaining in the material willexpand and formbubbles or pimples before it can escape.

The normal time requirement for completion of the drying and solidifyingprocess is approximatelythirty' minutes. -While the nor scraped.-Whenfinished in thismanner the surface assumes a natural high polish orgloss superior to that which can be given to the material by bufling ormechanically polishing.

While the heretofore method or process is that preferred, the coating ofarticles may be carried out by a variation of this process which isdesirable especially in those instances wherein it is impractical tosubject the coated article to the influence'of a thermal control fluid.In carrying o'ut the alternative process, the material is reduced toliquid form, the liquid being sufficiently heavy that a fairly heavycoating'will be deposited when operating in a room at approximatelyeighty degrees Fahrenheit. The liquid pyroxylin or analogous materialsare very sensitive to temperature change. After being dipped and thesurplus material drained, the dipped article is immediately removed to aroom having a low temperature of approximately zero Fahrenheit, whereinthe liquid becomes sufiiciently solid to greatly retard if not toentirely stop further flow or drain. At such low temperature, anymoisture remaining in the air will be deposited as frost, and not aswater. Even though the temperature of the coated article is materiallylowered by evaporation of the solvent, which process however is muchretarded at such low temperature, the temperature of the coated surfacewill not be less than. the room at zero temperature, and therefore willnot tend to attract condensation. In any event, it has been found thatfrost deposits do not mar the finish. At such low mperature theevaporation progresses slow and there is no inclination for theremaining solvent to expand, and therefore bubbling and pimpling' isentirely obviated. A much greater time is required for the material toset and harden at such low temperature. The time factor may be reducedand the process of evaporation of the solvent and consequent setting ofthe material may be materially accelerated by employing in such coldroom, gases whichwill facilitate evaporation, particularly such gases ashelium. hydrogen and the like. The coated article is preferably rotatedduring the cooled treatment process to insure uniformity of the deposit,as well as inthe process first described. The last described process ismore difficult from the production point of view, and the difficultiesof handling at low temperatures as well as the increased period oftreatment. The control of temueratureof the material posited coatingwhereby the exterior film is maintained suificiently soft to permit theescape of solvent from the underlying strata and conse uent preventionof premature surface shrin age and resulting wrinkling.- It is to beunderstood that the specific temperature degrees, ranges of temperature,and relation of temperature, while they are those found by experiment toproduce satisfactory results, are here stated for illustrative purposesand with no intent to unduly limit or restrict the scope of theinvention to such specific temperature degree, range and relation"beyond the broadest valid and legitimate interpretation of thehereinafter stated claims.

From the above description it will be apparent that there is thusprovided a device of the character described possessing the particularfeatures of advantage before enumerated as desirable, but whichobviously is susceptible of modificatidfi in its form, proportions,detail construction and arrangement of parts without de arting from theprinciple involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has beendescribed in language more or less specific as to structural features,it is to be understood that the invention is not limited to the specificdetails shown, but that the means and construction herein disclosedcomprise the preferred form of several modes of putting the inventioninto effect and the invention is, therefore, claimed in any of its formsor modifications within' the legitimate and valid scope of the appendedclaims.

Having thus described my invention, I claim: V

1. The herein described method of coating an article with anitrocellulose material comprising dissolving the material into aviscous liquid, dipping the article therein, and subjecting the dippedarticle to the influence of a temperature control medium of greatertemperature than the applied coating during the periodof rapidevaporation of the solvent and subsequently oflower temperature than theapplied coating to retardevaporation and swelling of the coating byexpansion of entrapped solvent.

2. The herein described method of surface coating articles with a liquidcoating material containing a volatile solvent comprising dipping thearticle into a bath of liquid coatdipping the article into a bath ofliquid coating material, draining the article and subj ecting it whiledrying to a temperature control medium having a temperature intermediatethat induced by the evaporation of the solvent and the room temperature.

at. The herein described method of surface coating articles with aliquid coating material containing a-volatile solvent including dippingthe article into a bath of liquid coating material, draining the articleand subjecting it while drying to a temperature influence somewhat lessthan the room temperature in which the drying is effected.

5. The herein described method of surface coating articles with a liquidcoating material containing avolatile solvent including dipping thearticle into a bath of liquid coating material, draining the article andmaintaining the article while drying, under temperature condition lessthan the room temperature sufficiently high to prevent'moistur'econdensation thereon, and sufliciently low to prevent expansion ofentrapped solvent within the coating. I

6. The herein described method of surface coating articles with a liquidcoating material containing a volatile solvent, comprising dipping thearticle into a bath of liquid coating material, and subjecting thearticle to drying temperature of approximately fifty-two degreesFahrenheit, and simulta neously subjecting the article to'the influenceof a temperature medium of approximately forty-six degrees Fahrenheit.

7. The herein described method of surface coating articles with a liquidcoating material containing a volatile solvent, comprising dipping thearticle into a bath of liquid coating material and drying the coatingwhile subjecting the article to a'temperature influence somewhat lowerthan the room temperature in which drying is effected.

8. The herein described method of surface coating articles with a liquidcoating material containing a volatile solvent, comprising dipping thearticle into a bath of liquid coating material and subjecting thearticle While drying to a uniform temperature condition initially ofhigher degree than the temperature of the coating immediately afterdipping while rapid evaporation of the solvent is being efi'ected, andsubsequently lower than the temperature of the coatingmaterialsubsequent to such period of rapid evaporation during the dryingperiod.

9. The herein describedmethod of surface coating hollow articles with aliquid coating containing a volatile solvent comprising dipping thearticle into a bath of liquid solvent, draining the dipped article, andcirculating through the interior of the hollow coated article atemperature control medium having a lower temperature than thesurrounding atmosphere. 1

10. The herein described method of surface coating hollow articles witha liquid coating containing a volatile solvent, comprising dipping thearticle into a bath of liquid solvent, draining the dipped article, andcirculating through the interior of the hollow coated article atemperature control medium having a temperature influence of within therange of forty-two to fifty-two degrees Fahrenheit while maintaining thesurrounding atmospheric temperature within a temperature range of fromfifty-four degrees Fahrenheit downwardly to that of the control medium.v

11. The herein described method of surface coating hollow articles witha liquid coating containing a volatile solvent, comprising dipping thearticle into a bath of liquid solvent, draining the dipped article, andcirculating through the interior of the hollow coated article atemperature control medium having a temperature, less than that of thesurrounding atmosphere but greater than the temperature developed by theevaporation of the solvent.

12. The herein described method of 'surface coating tubular shafts witha liquid coating containing a volatile solvent, comprising dipping theshaft into a bath of liquid coating material, draining the dipped shaft,giving to the shaft a rotary motion during a drying period andsimultaneously discharging through the shaft a temperature controlmedium. of lower temperature than that of the surrounding atmosphere.

13. The herein described method of surface coating tubular shafts with aliquid coating containing a volatile solvent, comprising dipping theshaft into a bath of liquid coating material, draining the dipped shaft,and drying the shaft while circulating therethrough a temperaturecontrol medium having a temperature below that of the coating materialinto which the article has been dipped.

' 14. The herein described method of surface coating articles withliquid coating material containing a volatile solvent, including sandblasting the surface to be coated, dipping the article into a bath ofliquid coating material, draining the excess material therefrom andtemporarily warming the coating material to counteract the refrigeratingeffect of rapid evaporation of the solvent, and subsequently mamtainingthe temperature of the coating below that of the surrounding atmosphereuntil such coating has solidified. In testimony whereof, I have hereuntoset my hand this 22nd day of May A. D. 1929.

WILLIAM C. HAMPTON.

